The present invention relates generally to light reflectors for exterior automotive lighting applications and more specifically to a multi-faceted light reflector having each facet aligned in a predetermined manner to obtain a desirable aggregate light distribution.
Several methods are used for controlling the light distribution from a light reflector. In U.S. Pat. No. 4,825,343, a projector headlamp is disclosed which uses a reflective surface which has a series of minute planar face elements for directing light from a light source in front of the reflecting surface to a predetermined region on a shade. The shade is used to mask a portion of light output. The face elements are arranged in a series of adjacent vertical columns to form the reflective surface. Each face element in a vertical column is aimed at a common point on the shade.
The '343 patent has several embodiments which describe the mirrored surface as having distinct regions which provide a function with respect to the light in different ways. The functions of some of the regions change drastically from their adjacent regions. These drastic changes in function generally result in either a discontinuity between adjacent vertical columns or a misdirection of light. One drawback to such a system is that light distribution cannot be precisely controlled since a shade must be employed to block out a portion of the light output from the bulb, i.e., light having an upward directional component. Another drawback to such a system is that discontinuities between the individual steps on the base structure surface promotes the buildup of reflective coating which is adhered to the surface by spraying which in effect causes uncontrolled and unpredictable light scattering. Yet another drawback to such a projector type headlamp is that the light pattern is of such a shape that a convex lens must be employed to obtain a proper light distribution pattern.
Another U.S. Pat. No. 4,704,661, describes a multi-faceted headlamp reflector having distinct bending and spreading facets formed of parabolic sections. The parabolic facet size is a function of the amount of bending and spreading required. Because the parabolic section size is directly dependent on its function, the overall package size is fixed which allows little flexibility in overall design. Another drawback to such a configuration is that distinct steps are formed by the bending and spreading facets. The stepped facets have the drawback that when the facets are sprayed with reflective coating, the reflective coating tends to build up on the corners of the edges of each step and cause an uncontrolled diffusion of the light.
In automotive design, lighting engineers are typically given a package design to work within. Lighting engineers are increasingly given reduced package sizes while still having to maintain a required light distribution. It would therefore be desirable to provide a light reflector without having stepped surface to control the light output.